The study is designed to evaluate the significance of tumor associated macrophages in the control of tumor growth and metastasis. Quantitation and distribution analysis of macrophages, T and B lymphocytes in tumors from patients with mammary carcinoma and from rats with mammary carcinoma will be performed by immunohistology with specific cell antisera and by opsonic adherence of sensitized erythrocytes on frozen sections. Quantitation of cell subpopulations of disaggregated human and rat tumors also will be performed. The data will be correlated with growth rate and degree metastasis of the tumors. Functional studies of macrophages present in murine methylcholanthrene induced fibrosarcomas will be performed by specific depletion of macrophages, T-lymphocytes or B-lymphocytes from tumor cell suspensions and repropulation with defined lymphoid cell popuations. Growth rate and metastasis from subcutaneous injection sites by those defined tumor cell suspensions will be compared with the behavior of unaltered tumor cell suspensions.